What is a Map?

A map is a representation of a selection of real features on the Earth. It is designed to record the
relationships between features and to allow these relationships to be analysed.

A map may be very simple (e.g. a sketch showing the location of plants in your garden) or very complex
(e.g. a topographic map of the Australian Alps).

Some key characteristics of maps are:

 maps portray, as accurately as possible, the spatial relationships between features – that is,
where a feature is located relative to other features.

 maps are drawn to a scale (although this may vary across the map – especially for ancient maps
and simple sketches).

 maps emphasise and omit certain features, depending on their design goals.

 As a general rule, a map is usually a two dimensional representation (e.g. a ‘flat piece of paper’)
of a three dimensional object (e.g. the Earth). However, occasionally the map may be a three
dimensional object, such as a globe.

 maps use mathematical formulae to represent the Earth (an irregularly shaped sphere) onto this
other surface.

 maps generally have a reference system which allows the location of a feature to be described.
For example, latitude and longitude are used as a reference system on maps of the Earth.

Up to late last century, maps were traditionally reproduced as ‘hard copies’ onto paper, parchment, film
etc. From the 1980s on, digital maps have emerged for use on the web and in Geographic Information
Systems

Types of Maps

There are many different types of maps, which are usually classified according to what they are
attempting to show.

However, it must be noted that there are many different ways to interpret the types of maps. One
common point of view is that there are two main types of maps:

 those which summarise the actual landscape (topographic and general reference maps); and

 those which describe ⁄ comment on specific features using the landscape as a background or for
context (all other maps – usually called thematic maps).

For ease of describing functionally quite different maps; and to explain what can be confusing
differences; we have opted to use a greater number of map types.

1. General Reference Maps

These are simple maps showing important physical (natural and man–made) features in an area. Their
main purpose is to summarise the landscape to aid discovery of locations. They are usually easy to read
and understand. Most of the early mapping of the Earth falls into this group.

General Reference maps often enlarge or emphasis some features to aid users. For example, road maps
show roads boldly and may use road widths and colour to distinguish between major and minor roads.

As a general rule, General Reference Maps would only show relief (the difference in height between
features on the map) in a stylised manner. Street and tourist maps are good examples of general
reference maps.

A typical late-20th
century general reference map of a country:
- is colourful
- cities are named
- major transport routes (highways and railways) are identified
- natural features such as rivers, lakes and mountains are named
- elevation is shown using a simple colour shading
- has themes included – eg city population size

Topographic Maps
Introduction

Like General Reference Maps, Topographic Maps are a summary of the

landscape and show important physical (natural and man-made) features in
an area. The primary difference is that they show elevation in detail.
Characteristics of topographic maps include:

 they show elevation using contour lines. Put simply, a contour line is a line
which joins points of equal elevation above sea level
 they have an emphasis on showing human settlement (roads, cities,
buildings etc), but may include some thematic information such as
vegetation or the boundaries of national parks
 they are typically produced by government agencies – these are often
specialist mapping agencies and may have either a civilian or defence
purpose
 they have well defined standards (called Specifications) which are strictly
adhered to – these vary between mapping agencies and the scale of the
map
 they have very good location reference systems – including latitude and
longitude, but may also have grid lines
 often have additional information such as an arrow pointing to Magnetic
North as well as True North.

As there is an exceptionally large amount of information about Topographic

Maps available online (more so than any other form of mapping) we shall give
a very simple overview of it. See Further Reading below.

Topographic maps are usually part of a series of maps, but may be one–off /
stand–alone maps.

Understanding Contours
This extract from a 1:50,000 scale map has been annotated in pink to highlight different landscape
features which can be identified using the contour lines. This map had a contour interval of 20 metres.

Elevation is usually shown using contour lines. In simplistic terms a contour

line is a line which joins points of equal elevation. Where these lines are
above sea level they are simply called contour lines and where they are below
sea level they are called bathymetric contour lines.

Contour lines can tell an informed reader many things about the shape of the
land and its ruggedness. The closer contours are together the steeper the
land and the further they are away from each other the flatter the land. On the
Nullarbor Plain, for instance, very few contour lines would be shown, but over
the Snowy Mountains an enormous number of contour lines would be shown.

A word of warning: topographic maps do not show every contour line, rather
they choose sample of the lines. For example every 20, 50, 200 metres –
depending on the scale of the map. This is called the contour interval of the
map. As a result of this selection process, the difference in density of the
contour lines is only indicating relative changes in the shape of the landscape
– on that map!

The reading of topographic maps and interpretation of contour lines, is a much

written about topic. Please refer to the Further Reading hyperlinks to learn
more about contours and understanding what they mean.

A bit of history: Contours were developed in the 19th century (1800s). Prior
to this, various systems of drawing the relief had been experimented with,
including a system called hachuring. These systems have largely disappeared
from modern map making, but they are intriguing to read about. This site from
the University of Portsmouth has a very interesting historic summary of the
changes over the
years: http://www.geog.port.ac.uk/webmap/hantscat/html/ftr_hil.htm

→ Read more about contours in A Map Users Guide to Reading Tactual and Low
Vision Maps.

Topographic Maps as a Summary of the Landscape – an example

This topographic map and photograph are of the same area – the Manly
region within Sydney, NSW. By comparing these two it is clear that the map is
an excellent summary of the landscape of the area. Note that the features
which dominate the photograph also dominate the map. And, because it is a
topographic map, it also gives detailed information about the ‘bumpiness’ of
the land.

Topographic map of the Manly region within Sydney, NSW.

Satellite view of the Manly region within Sydney, NSW.

A 'Potted' Geography of Australia using Topographic Maps

Four maps have been selected across Australia to illustrate the vast range of
information which can be contained in a topographic map. These maps are all
part of a series of maps which cover the whole of Australia and they have been
produced using the same specification – i.e. any difference in appearance of
the map is the result of a difference in the landscape.

This map is centred on the Pilbara region mining town of Paraburdoo. The area is lightly settled and
poorly vegetated. Because of this, the features shown on the map are less obscured compared to other
parts of Australia. In particular, the contour lines (shown in brown) are easily seen – where they are
close together the slope is greatest. Note the ranges (lines of hills) crossing this map. Also note that the
sparse settlement in this region is indicated by the small number of roads and towns/buildings.
This map is centred in a broad–acre agricultural area (often called a wheat ⁄ sheep area) north of Perth,
Western Australia. Here the contour lines are far apart indicating gently sloping land and, because there
are no contours close together, it is clear that there are no ranges. A denser settlement than our first
example is indicated by the larger number of roads and the buildings (the black squares) which are
shown.

This third map is in the wet tropical region around Darwin, Northern Territory. There are very few
contour lines, indicating that the land is very flat. Also, the much denser settlement is indicated by the
large number of buildings and the large city area (the area in pink – here the houses are too close
together to be shown separately – in mapping jargon this is called a built-up area).
A feature present here that has not been shown on the other two maps is vegetation. This doesn't mean
that there is no vegetation on the other maps, rather they have simply opted to not show it or the
vegetation is less dense. Forested land is shown in light green and mangrove areas in dark green. Please
note that this adds colour to the map, but can make the contour lines hard to see.
Finally, this fourth map is over Sydney, NSW. With a population of over 4 million people, this is
Australia's largest city. The contours are close together, indicating hilly land. The city area covers a large
part of the map and there are a large number of buildings shown surrounding the city. The road network
is also very complex.

Explaining Some Jargon – Topographic Map Numbering Systems

For series maps, particularly topographic series maps, a variety of map

conventions have been developed. One which can be confusing is the
different map numbering systems.

In series maps it is essential that individual maps should be easily and

uniquely identifiable. Map name alone is not sufficient to easily identify and
locate an individual map. This is especially a problem where there are a large
number of maps in a topographic map series. For example in Australia there
are:

 513 individual 1:250,000 scale topographic maps, and

 3,066 individual 1:100,000 scale topographic maps
This problem was partly solved by the development of a numbering system for
the International Map of the World (IMW). This system hinged on two features:

 a well defined, regular, smaller scale grid was developed for the whole
Earth’s surface
 larger scale maps were 'nested' inside this grid

It was agreed that the smaller scale grid should be for 1:1,000,000 (often
called 1:1 million scale) topographic mapping. The 'nested' smaller scales
were 1:250,000, 1:100,000, 1:50,000, 1:25,000 etc.

The International Map of the World and its Numbering System

In 1891 the Fifth International Geographical Congress agreed on the

development of a world-wide, 1:1,000,000 (or 1:1 million) scale series of
maps. This was to be called the International Map of the World (or IMW for
short). The maps were to be produced using an internationally agreed, consistent
specification.

For several reasons the development of the IMW maps was slow – reasons
included two World Wars, the Great Depression and lack of funding in poorer
countries. International interest waned and by the 1980s only 800-1000 of the
proposed 2500 maps were completed. The project was abandoned by the
mid-1980s. The Australian component of the IMW was 49 maps. Work on
these began in 1926 and was completed in 1978.
This is the index for the IMW maps which cover Australia. Note that each IMW map/zone has:
- unique name
- is located in an IMW latitudinal zone (starting with the letter C in the North and ending with the letter K
in the South)
- is located in an IMW longitudinal zone (starting with the number 49 in the West and ending with the
number 56 in the East)

The enduring legacy of the IMW map series is its map numbering
conventions. The regular grid it developed consisted of:

 4° wide latitudinal zones for the whole earth numbered A to V, away

from the Equator; and with the letter N or S (to identify either the Northern
and Southern Hemispheres).
 6° wide longitudinal zones were for areas between the latitudes 60°
numbered 1 to 60, East to West starting at the 180°
 12° or 24° wide longitudinal zones between the latitudes 60° and 90°.
Using this method a regular grid was created, and each had a unique number.
For example, in the case of Sydney, Australia, its IMW grid cell (variably
called an IMW zone, IMW map zone or IMW map) would be identified as:

 S – for the Southern Hemisphere

 J – for the latitudinal zone it belongs to
 56 – for the longitudinal zone it belongs to

Add the three together and Sydney, Australia is found in the IMW zone of
SJ56. This numbering systems allows a map user to locate a map anywhere
on the surface of the Earth – using only the number as a guide.

In addition to this, each IMW map zone is uniquely named. In the case of the
Sydney, Australia example the map sheet is SJ56, Sydney. Where the extents
of a map are different to the standard IMW zones (to totally cover a city) the
word 'Special' is added to the map name.

Numbering 1:250,000 Scale Topographic Maps

The next step in the numbering system is easy – based on convention, there
are 12 individual 1:250,000 scale maps in an IMW zone. These are each
numbered 1–12 in a regular pattern. This is added to the IMW zone number
and another unique number is created. In the case of the Sydney example
above, the IMW map sheet is SJ56 and the 1:250,000 scale map called
Sydney the 5th map in the zone – ie the Sydney 1:250,000 scale map is
numbered SJ56-5.

Numbering Other Scale Topographic Maps

Similar principles of a unique numbering system which had been developed

for the 1:250,000 scale series topographic maps were also developed for the
1:100,000, 1:50:000, 1:25,000 scale series topographic maps.

The 1:100,000 scale topographic maps were nested within the IMW system.
There are six 1:100,000 scale maps contained within a 1:250,000 scale map.

In this case the system involved:

 using a two digit number which is sequentially given to each 1:100,000

scale map West-to-East
 using a two digit number which is sequentially given to each 1:100,000
scale map South-to-North
This results in a unique 4-digit number for every 1:100,000 map within the
system.

As with the 1:250,000 scale maps having a number based on the number of
IMW zone they are in; so to do the 1:50:000 and 1:25,000 maps. They have a
sequential number added to the number of the 1:100,000 map they occur in.

Note. This system is used for Series Topographic Maps by Australian

government mapping agencies. However, the old saying of "always expect the
unexpected" applies. Some agencies use systems which are based on the
IMW grid, but they may be slightly different.

Also, this regular grid system creates a number of maps which cover small
amounts of land and large amounts of landless ocean. Many mapping
agencies 'move' the map boundaries to maximise the amount of land which is
shown.

Below are two indexes for mapping over north-western Australia. The top one
is the the International Map of the World (IMW) topographic maps. The bottom
one is for the World Aeronautical Charts (WAC) map series. Note how the
WAC charts have been adjusted to maximise the amount of land they cover.
IMW Map Index

Both the International Map of the World (IMW) and the World Aeronautical
Charts (WAC) are international map series which show topographic
(especially elevation) information.

The IMW topographic map series was developed in the early 1900s and the
WAC series was developed in the mid–1900s. As an Internationally agreed
series with a standard specification and a regular map grid, the IMW was the
'first of its type in the world.
 This is an example of a
map which is usually called a tourist map. It is a General Reference Map which has been enhanced for a
specific reason – that of highlighting places of interest that people might like to visit. Because of this, it
can also be described as a thematic map (the theme being tourism).

Image courtesy of Mapland, Department of Environment, Water and Natural Resources, SA.
 The Street Map is well
known to all maps users, indeed it may be the only map some people use. Street maps contain all the
elements of a general reference map in that they are a summary of the landscape and that their primary
purpose is to aid in the discovery of a location. In this example of a street map, individual buildings are
identified.